Ingredients

1 tbsp. unsalted butter

0.50 lb. provolone cheese

2 large egg yolks

1 tbsp. all-purpose flour

1.50 c. whole milk

Salt and pepper to taste

Directions

Fill the bottom of a double boiler halfway with water and place over medium heat. Melt the butter in the top of the double boiler. (If you don't have a double boiler, melt the butter in a stainless-steel bowl set snugly inside a saucepan filled with a few inches of water.) Add the cheese and let it soften slowly, stirring.

Meanwhile, in a medium bowl, whisk together the egg yolks, flour, and milk. When the cheese has melted, pour the egg mixture into the top of the double boiler and whisk until the sauce is warm and begins to thicken. Continue to cook over medium heat, whisking constantly. Add salt and pepper to taste. When the sauce is thick, turn the heat to low to keep it warm while you assemble the sandwiches. Use immediately. Cover and refrigerate any leftover sauce.